Strobe light system for transitional guidance and delineation

ABSTRACT

A strobe light system including a plurality of strobe light assemblies which may be positioned along a highway at spaced intervals to provide road delineation, and particularly guidance of vehicular traffic from one lane to another around obstacles such as construction, accidents, and the like. Each strobe light assembly includes a lamp unit and a circuit housing mounted on a portable stand. Circuitry for controlling the flashing of the lamps in master or slave modes, and for providing fail safe operation is mounted in the circuit housing. Each assembly further includes a jumper cable for connection to a primary cable connected to a power source. Each jumper cable includes calibration markings to enable accurate positioning of the assemblies for transitional purposes.

United States Patent Doughty 1 1 STROBE LIGHT SYSTEM FOR TRANSITIONALGUIDANCE AND DELINEATION [75] Inventor: Frederic C. Doughty, TredyffrinTownship Chester County, Pa.

[73] Assignee: Elco Corporation, Willow Grove,

[22] Filed: Apr. 2, 1973 [21] Appl. No.: 347,257

[52] US. Cl 315/312, 174/112, 315/210, 315/313, 315/323, 340/46, 340/82,340/114 [51] Int. Cl. H05b 37/02, H05b 41/44 [58] Field of Search174/69, 70 R, 70 A, 112; 307/246, 252 M, 293; 315/209 R, 210, 211,

340/41 R, 41 A, 46, 82,114 R, 114 B, 331,

[4 1 Nov. 5, 1974 OTHER PUBLICATIONS Rome Underground Report, ElectricalWorld, Vol. 166, No. 26, Dec. 26, 1966, page 62.

Primary Examiner-Herman Karl Saalbach Assistant ExaminerE. R. LaRocheAttorney, Agent, or FirmAlan L. Newman, Esq.

[57] ABSTRACT A strobe light system including a plurality of strobelight assemblies which may be positioned along a highway at spacedintervals to provide road delineation, and particularly guidance ofvehicular traffic from one lane to another around obstacles such asconstruction, accidents, and the like. Each strobe light assemblyincludes a lamp unit and a circuit housing mounted on a portable stand.Circuitry for controlling the flashing of 341 the lamps in master orslave modes, and for providing fail safe operation is mounted in thecircuit housing. [56] References cued Each assembly further includes ajumper cable for UNITED STATES A E S connection to a primary cableconnected to a power 3,046,521 7/1962 Cantwell r al 340 41 source. Eachjumper cable includes calibration mark- 3,384,871 5/1968 Selzer et a1.340/41 ings to enable accurate positioning of the assemblies 3,488,5581/1970 Grafton 315/312 for transitional purposes.

FOREIGN PATENTS OR APPLICATIONS 7 Claims, 5 Drawing Figures 275,2509/1927 Great Britain 174/112 [48 5O 52 FROM, VOLTAGE vriifriiee EEREGULATOR GENERATOR IN/i MASBTER Lr FAIL SAFE j TRIGGER 58 so 62 r64INPUT L DELAY OUTPUT PULSE cmcun' SW TCH z i gg PATENTED NOV 5 I974SHEET 10F 2 BATTERY FIG.2.

IAIENTEHNHV Ian 3.846.672

- SNEH 2 0F 2 HIGH gg VOLTAGE VOLTAGE LAMP SUPPLY REGuLAToR I GENERATORUNIT 54 56 MASTER I a' TRIGGER FAIL SAFE OUTPUT INPUT DELAY L SWITCH LTO NEXT PULSE CIRCUIT a i-35 LA NIP AGGY 552 FIG 5 LAMP UNIT voTT /FGE lL88 96V]- cc i 74 T 58 64 Vcc '02 5g DELAYED l1; 8 f T f 2 MONOSTABLE JMONOSTABLE TO NEXT F- W 7 x76 82; 5 MV LAMP 4 ASS'Y IFNRPOUJ NO DELAY 5"JI O0 84 Z PREVIOUS )6 LIGHT ASS'Y o 1 STROBE LIGHT SYSTEM FORTRANSITIONAL GUIDANCE AND DELINEATION BACKGROUND OF THE INVENTION Thisinvention relates to strobe light delineation systems and moreparticularly to a strobe light system for vehicular transitionalguidance.

Various approaches have been utilized to provide transitional guidanceto motorists around obstacles on the road such as construction,accidents, etc. Such approaches have included barricades, series ofbarricades progressively positioned further onto a traffic lane,individual flashing lights, flashing lights in the form or arrows,signs, and various combinations of the above. These systems, however,are not entirely satisfactory because they primarily only warn themotorist of obstacles ahead rather than actually guide him into anotherlane around theobstaclewhile some guidance is given by signs andprogressively positioned barricades, the placement of such devices isawkward and time consuming, and visibility may be impaired by poorweather conditions, darkness, or poor placement of them. In summary,these systems do not provide clearly defined, easily visible guidance tothe motorist especially on high speed roadways.

Strobe light systems per se have been utilized for aircraft landingguidance. One example of such a system is disclosed in the Zychal US.Pat. No. 3,519,984, which is owned by the assignee of the presentinvention. While Zychal was a substantial improvement over the prior artat the time, it was primarily designed for use as a portable landinglight system, and therefore, would require modification for use onroadways. In addition, it has several disadvantages such as the relianceof each light assembly on the flashing of its immediately precedinglight assembly to cause it to flash, and the lack of fail safeprotection.

SUMMARY OF THE INVENTION The present invention overcomes thedisadvantages of the prior art by providing a novel strobe light systemwhich gives early, clearly defined guidance to the motorist, may beeasily and quickly installed, and includes provisions to allow accuratepositioning quickly and simply. This is accomplished by providing aplurality of strobe light assemblies, detachably connected to a primarycable to which a power source is connected. Each strobe light assemblyincludes a portable support stand on which is mounted a circuit housing,a lamp unit, and a jumper cable for connection to the primary cable.Each jumper cable includes calibration markings so that the stands canbe accurately positioned relative to the road to provide accuratepositioning for transitional guidance. Each assembly also includeselectronic circuitry accessably mounted in the circuit housing fortriggering the strobe lamp unit, providing master or slave operation andfail safe protection. The circuitry may be easily switched to masteroperation at either of two rates, or to slave operation for simultaneousor sequential flashing.

It is therefore a general object of the present invention to provide astrobe light system which overcomes and minimizes the disadvantages ofthe prior art.

It is a more specific object of the present invention to provide astrobe light system in which the sequential flashing of each lightassembly does not depend on the flashing of previous lamp units.

It is another object of the present invention to provide a strobe lightsystem which includes fail safe protection. It is still another objectof the present invention to provide a strobe light system which isreadily selectively-adjustable to various modes of operation.

It is a further object of the present invention to provide a strobelight system for vehicular transitional guidance which may be easily andquickly installed. It is still a further object of the present inventionto provide a strobe light system for vehicular transitional guidancewhich is easily and readily accurately positioned on a roadway.

BRIEF DESCRIPTION OF THE DRAWINGS These, as well as other objects of thepresent invention, will become apparent to those skilled in the art froma persual of the appended claims, and the following description whenread in conjunction with the attached drawings in which:

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIGS. 1-3a preferred embodiment of a strobe light system of the presentinvention, generally designated 10, includes a plurality of lampassemblies 12 which are connected through individual jumper cables 14 toa primary cable 16 which in turn is connected to a DC power supply 18.The DC power supply 18 may be of any conventional type for converting ACpower derived from an available source, such as overhead wires, and/or abank of batteries 20 which may be connected to supply power in case offailure of the AC source. The primary cable 16 may be made up ofindividual sections of cable 22 having connectors or junction boxes 24to allow connection to the next section of cable, and also to receive aconnector 26 at the free end of the jumper cables 14.

Each of the light assemblies includes a portable support stand 28 havinga base 30, and a light support shaft 32; a circuit housing 34, having anopenable lid 36 mounted on top of the support shaft 32; and a lamp unit38 electrically connected to circuitry mounted in the circuit housing34. The lamp unit may be any conventional strobe light such as a xenonflash tube available under various designations such as governmentaldesignation STUS.

Each light assembly 12 also includes the jumper cable 14 which isconnected at one end to the circuit housing 34 for electrical connectionto a circuit therein, and may be coiled around an outwardly extendingmember 40 mounted axially along the support shaft 32.

In order that the flashing lamps be clearly visible to oncoming traffic,it is important that they be accurately positioned so that anuninterrupted moving point of light, when the units are operating insequence or a flashing line when the units are operating simulta- 1neously, be clearly visible to oncoming traffic.

In the present invention such accurate positioning is accomplished bycalibration markings 42 provided on the jumper cable 14. For accurateplacement the markings 42 are successively aligned with the road edge orlane edge. That is, the first marking 42 of the first light assembly 12is aligned with the edge, the second marking 42 of the second lightassembly 12 is aligned with the edge, etc. The markings are spaced sothat with the full system set up the last light assembly is at the otheredge of the lane from which traffic is being guided. For example in FIG.3, the eleventh calibration marking is aligned with the edge between aright lane 44 and a road berm 46, inasmuch as the right lane is to befreed of traffic as shown in FIG. 1.

By virtue of the calibration markings on the jumper cables 14, the lineof light assemblies 12, created when the system is set up, accuratelyfollows the curvature of.

the roadway, thereby creating highly visible vehicular guidance. Thenovel physical structure of the present invention, described above,provides a number of advantages in addition to the accurate positioningof the light assemblies 12 already discussed. First, the system isquickly and easily deployable by merely reeling out the primary cable16, setting individual light assemblies 12 adjacent to the junctionboxes 24, connecting the primary cable 16 to the DC power supply 18,connecting the individual light assemblies 12 to their respectivejunction boxes 24, and accurately positioning the light assemblies 12 onthe roadway as discussed previously. Furthermore, the entire system canbe set up and operating on the side of the road before moving it ontothe roadway, thereby allowing the guidance to be gradually imposed ontraffic, and providing maximum safety for the set-up crew.

In addition, the fact that each light assembly 12 is identical exceptfor perhaps the first assembly, which will typically be operated inmaster mode, eliminates any requirement for putting particularassemblies at specific locations. Finally, the accessible nature of thecircuitry and the mode switch, discussed in detail hereinafter, allowsthe mode of operation to be easily changed, and also permits easyservicing or repairs of the circuitry.

In the present invention each light assembly 12 may be operated as amaster in which it flashes at a preset rate independently of other lightassemblies, or as a slave in which it flashes in response to an inputpulse received from the preceding light assembly R. In the preferredembodiment a choice of two flash rates is provided for master operation,and a choice of either sequential or simultaneous operation is providedin the slave operation. Typically the light assembly closest to oncomingtraffic will be operated as a master with the remaining light assembliesin the slave mode either simultaneously or sequentially. If operatedsequentially, a point of light will appear to move down the lane guidingtraffic to the next lane. If operated simultaneously, a full line oflight will appear to flash on and off at the same time. If, however, thefirst assembly were inoperable to provide a master signal, it could beswitched with any of the other assemblies inasmuch as they are allinterchangeable. The only change that would be required would be tomanually alter the switch position within the circuit housing 34.

The novel circuitry mounted in the circuit housing 34 of each lightassembly 12 provides the various modes operation, and permits the easyselection of the desired mode. The circuitry also includes fail safeprotection so that if the assembly is switched to the slave mode, but noexternal pulses are received, a fail safe pulse is provided to flash thelamp. One embodiment ofcircuitry suitable for these purposes isillustrated in block diagram in FIG. 4.

Referring to FIG. 4, a voltage is fed from the DC supply 18 to a voltageregulator 48, which may be for example a Fairchild UA7812. The output ofthe voltage regulator 48 is fed directly or through a voltage dividerand a zener diode combination, not shown, (if required to produce thenecessary voltage level) to supply a low voltage for operatingintegrated circuitry to be discussed later. The output of the voltageregulator 48 is also fed to a high voltage generator 50 which may be aconventional blocking oscillator with a step-up transformer. The outputof the high voltage generator is supplied to a lamp unit 52 and to amaster and fail safe unit 54 and a trigger 56 which will be discussed ingreater detail hereinafter with respect to FIG. 5. The high voltagegenerator typically has an output voltage on the order of 350-400 volts,the level necessary to energize the lamp unit 52. The system alsoincludes an input pulse terminal 58 for receiving a pulse from apreceding light assembly which is connected to supply received pulses toa delay circuit 60, the output of which is supplied to a switch 62.

The switch 62, as will be discussed in detail hereinafter, is connectedto the master-fail safe unit 54, and the trigger 56 to determine themode of operation. The output from the switch that is supplied to thetrigger 56 is also supplied to an output pulse shaper 64, which providesan output pulse to the next light assembly. The output pulse shaper 64is also connected to the trigger 56 so that it will receive an inputsignal if the circuitry is operating in its master mode.

In operation the DC voltage supplied from the DC supply 18 is regulatedby the voltage regulator 48, and is stepped-up by the high voltagegenerator 50 to supply the lamp unit 52, as well as the master and failsafe 54 and the trigger circuit 56 with operating voltage. The regulatedvoltage may be stepped down, if required, to supply the proper biasvoltage to semiconductor components in the circuitry.

As is conventional the lamp unit 52 includes a capacitor connected to atrigger electrode, which is rapidly discharged to flash the lamp. Thiscapacitor is connected to the trigger 54 which will discharge it inresponse to a pulse from either the input terminal 58 and delay circuit60 or the-master and fail safe 54, depending on the state of switch 62or the occurrence of a defect requiring the operation of the fail safe.The position of the switch 62 determines the mode of operation of thelight assembly, as discussed in detail hereinafter, through itsconnection to the master and fail safe 54 and the trigger 56.

The output pulse of the switch 62 which is supplied to the trigger whenthe switch 62 is in its slave position is shaped in the output pulseshaper 64 for feeding to the input pulse terminal 58 of the nextsucceeding light assembly. If the switch 62 is in its master position,an output pulse from the trigger 56 will be applied to the output pulseshaper 64 for the same purpose. It should be appreciated that in eitherslave or master mode, the

output pulse to be fed to the next light assembly is not dependent onthe flashing of the lamp itself. Therefore, any defect or lamp failurewill not affect the operation of subsequent light assemblies.

Inasmuch as the voltage regulator 48, high voltage generator 50, andlamp unit 52 are conventional and/or commercially available items theywill not be discussed in further detail. The remainder of the blockdiagram is shown schematically in FIG. 5.

Referring to FIG. 5, an input pulse from a previous light assembly isfed from the input pulse terminal 58 through a coupling capacitor 66 tothe delay circuit 60. The delay circuit 60 includes a monostablemultivibrator 68 which may be a SN54l2l available from Texas Instrument.The monostable multivibrator 68 is supplied with supply voltage VCC fromthe voltage regulator 48, and is suitably biased and timed. Themonostable multivibrator 68 has two outputs, namely a nondelayed signaloutput line 70, and a delayed signal output line 72. A pair of diodes 74are, respectively, connected between each of them, and the supplyvoltage Vcc to provide noise supression. Output pulses on each of thelines 70 and 72 are fed through coupling capacitors 76 to the switch 62.

The switch 62 includes eight terminals numbered 1 through 8 in FIG. 5,which are selectively interconnected by two sliding contacts 78 and 80,which are tied together to slide simultaneously. The delayed pulse line72 is connected to terminal 2, and the nondelayed pulse line 70 isconnected to terminal 7. Terminals 1 and 8 are both connected to thetrigger 56, and also to the output pulse shaper 64. Terminal 3 is anopen ter minal, and terminals 4 and 6 are individually connected throughcapacitors 82 and 84, respectively, to ground. Terminal 5 is connectedto the master 54.

The master and fail safe 54 includes an oscillator circuit whichcomprises a timing resistor 86 connected at one end to the high voltagesupply and at the other end to one end of a timing capacitor 88, theother end of which is connected to ground. A diac or trigger diode isconnected to the junction between the resistor 86 and the capacitor 88.The other end of the diac 90 is connected to the input point 91 of thetrigger 56, to which the terminals 1 and 8 of the switch 62, as well asthe output pulse shaper 64, are also connected. The trigger 56 consistsof an SCR 92 having its anode connected to the high voltage supply andthe discharge capacitor of the lamp unit 52 and its cathode connected toground. The gate electrode is connected through a resistor 94 to theinput point 91, and a capacitor 96 to ground, a resistor 98 is alsoconnected across the SCR.

The output pulse shaper includes a filter circuit 100 comprising asuitable resistor-capacitor network, and a monostable multivibrator 102which may be a SN54l2l available from Texas Instrument. The monostablemultivibrator 102 is suitably biased and tuned, and connected tobias'voltage Vcc.

In operation, as discussed previously, the lamp unit 52 will be flashedwhen the capacitor included in the unit is rapidly discharged. Thisoccurs when the normally off SCR 92 is turned on in response to a pulseat the trigger point 91, which applies a voltage to its gate electrode.This pulse will be fed through either the switching terminals 1 or 8, orthe master or fail safe 54.

The master and fail safe 54 merely operate as an oscillator to supplypulses to the trigger input point 91. That is, the timing capacitor 88charges up through the timing resistor 86 until the diac 90 is turnedon. If operating as a master, pulses will be supplied at a pulse ratedepending on the value of the timing capacitor 88 alone for the fastrate master, or by the value of the timing capacitor 88 together withthe capacitor 84 connected to the switch terminal 6 for the slow ratemaster. If operating as a fail safe, when the switch is in the slavemode, the pulse rate is determined by the valve of the timing capacitor88 and the capacitor 82 connected to the switch terminal 5. However, infail safe pulses will not be provided as long as the system functionsproperly, inasmuch as the much faster rate of pulses fed to inputterminal 58 will trigger the SCR 92 on thereby continuously dischargingthe capacitors 88 and 82 before they reach the level necessary to turnon diac 90.

For master operation at the slow pulse rate the switch is set with thesliding contacts 78 and 80 connecting terminals 2 and 3 and terminals 5and 6 respectively. With the switch 62 in this position neither delayedpulses on the line 72 nor the nondelayed pulses on the line are suppliedto the trigger input point 91. Rather the capacitor 84 is connected inparallel with the timing capacitor 88, as discussed previously. If thefaster rate master mode is desired, the switch 62 is positioned with thecontact 78 connecting terminals 3 and 4, and the contact 80 connectingterminals 6 and 7. In this mode there is no additional capacitor acrossthe timing capacitor 88, and therefore the master can oscillate at afaster pulse rate.

For sequential slave operation, the contacts 78 and 80 are positioned toconnect terminals 1 and 2, and terminals 4 and 5 respectively. In thisposition delayed pulses on the line 72 are coupled to the triggerjunction, and to the output pulse shaper 64. The pulse rate of this modeis solely dependent on the timing of the monostable multivibrator 68.Also in this position the capacitor 82 is connected in parallel with thetiming capacitor 88 to provide the oscillator with a potential pulserate much slower than the delayed pulse rate. This arrangement providesthe fail safe protection. For simultaneous slave operation, the contacts78 and 80 are positioned to connect terminals 4 and 5, and terminals 7and 8 respectively. In this position the master and fail safe 54 isagain set for fail safe, and nondelayed pulses on the line 70 areapplied to the trigger input point 91.

Thus, a unique and novel strobe light system has been disclosed. Whilethe detailed description has been directed primarily to the use of thesystem for transitional guidance, it will be apparent that the systemcould readily be utilized for other purposes as well. For example, itcould be permanently installed for road delineation and energized inresponse to a sensed condition such as fog, snow, etc. Such a use wouldonly require the connection of a suitable sensing device between thesource of power and the DC power supply so that the system would beenergized only when the condition is sensed.

The novel physical structure which is primarily directed to the use ofthe system for vehicular transitional guidance provides a system whichcan be quickly, easily, and safely set up, and which can be easilyaccurately positioned. The novel circuitry provides a system which isflexible, permitting the interchangeability of rality of strobe lightsinterconnected to form a system art. It will also be apparent that anumber of variations and modifications may be made without departingfrom its spirit and scope. Accordingly the foregoing description is tobe construed as illustrative rather than limiting.

What is claimed is:

l. A strobe light system for deployment along a roadway to providevehicular transitional guidance comprising:

a plurality of light assemblies, each of said light assembliesincluding;

a portable support stand,

a strobe lamp unit mounted on said support stand,

a circuit housing mounted on said support stand,

a jumper cable connected at one end to said assembly, and

circuit means mounted in said circuit housing for controlling theflashing of said strobe lamp unit said circuit means including triggermeans for causing said strobe lamp unit to flash, input means forreceiving an external pulse from the circuit means of a preceding lightassembly,

output means connected to said trigger means for supplying an externalpulse tothe circuit means of the succeeding light assembly whenever saidtrigger means receives an actuating pulse,

switching means for selectively connecting said input means to saidtrigger means, so that said external pulse actuates said trigger means,and

pulse generator means connected to said trigger means for providing anactuating pulse to said trigger means,

said switching means including means for controlling said pulsegenerator means to operate as a master trigger actuating pulse generatorwhen said switching means causes said input means to be disconnectedfrom said trigger means, and fail safe means for controlling said pulsegenerator means to operate as a fail safe trigger actuating pulsegenerator when said switching means causes said input means to beconnected to said trigger means; and

a primary cable which supplies operating voltage to and interconnectssaid circuit means of said light assemblies through the individualjumper cable associated witheach of said light assemblies.

2. The system of claim 1 wherein each of said jumper cables includescalibrated markings thereon to facilitate accurate positioning of thelight assemblies.

3. The system of claim 1 wherein said primary cable includes a pluralityof connectors spaced along its length,

wherein each of said jumper cables includes connector means at its otherend for connection to any one of said connectors, and

wherein said circuit housing is operable to provide easy access to saidcircuit means. I

4. A control circuit for operating each one of a pluin which theflashing thereof will occur in a desired manner comprising:

trigger means for causing a strobe light to flash,

input means for receiving an external pulse from the control circuit ofthe preceding strobe light,

output means connected to said trigger means for supplying an externalpulse to the control circuit of the succeeding strobe light wheneversaid trigger means receives an actuating pulse,

switching means for selectively connecting said input means to saidtrigger means so that external pulses received by said input means mayactuate said trigger means, and

pulse generator means connected to said trigger means for providing anactuating pulse to said trigger means,

said switching means including means for controlling said pulsegenerator means to operate as a master trigger actuating pulse generatorwhen said switching means is in a mode causing said input means to bedisconnected from said trigger means, and fail safe means forcontrolling said pulse generator means to operate as a fail safe triggeractuating pulse, generator when said switching means is in a modecausing said input means to be connected to said trigger means.

5. The circuit of claim 4 wherein said pulse generator means includes atiming capacitor for determining the pulse rate thereof said timingcapacitor being discharged whenever said trigger is actuated, and

eludes delaying means for delaying a received external pulse so as toactuate said trigger means after a time delay, when said input means isselectively connected through said switching means to create sequentialflashing of the strobe lights of the system.

7. The circuit of claim 6 wherein said input means further includesmeans for supplying a received external pulse to actuate said triggermeans without a time delay, so as to create simultaneous flashing of thestrobe lights of the system, and wherein said switching means mayselectively connect either said delayed external pulse or saidnondelayed external pulse or neither of said pulses to said triggermeans.

1. A strobe light system for deployment along a roadway to providevehicular transitional guidance comprising: a plurality of lightassemblies, each of said light assemblies including; a portable supportstand, a strobe lamp unit mounted on said support stand, a circuithousing mounted on said support stand, a jumper cable connected at oneend to said assembly, and circuit means mounted in said circuit housingfor controlling the flashing of said strobe lamp unit said circuit meansincluding trigger means for causing said strobe lamp unit to flash,input means for receiving an external pulse from the circuit means of apreceding light assembly, output means connected to said trigger meansfor supplying an external pulse to the circuit means of the succeedinglight assembly whenever said trigger means receives an actuating pulse,switching means for selectively connecting said input means to saidtrigger means, so that said external pulse actuates said trigger means,and pulse generator means connected to said trigger means for providingan actuating pulse to said trigger means, said switching means includingmeans for controlling said pulse generator means to operate as a mastertrigger actuating pulse generator when said switching means causes saidinput means to be disconnected from said trigger means, and fail safemeans for controlling said pulse generator means to operate as a failsafe trigger actuating pulse generator when said switching means causessaid input means to be connected to said trigger means; and a primarycable which supplies operating voltage to and interconnects said circuitmeans of said light assemblies through the individual jumper cableassociated with each of said light assemblies.
 2. The system of claim 1wherein each of said jumper cables includes calibrated markings thereonto facilitate accurate positioning of the light assemblies.
 3. Thesystem of claim 1 wherein said primary cable includes a plurality ofconnectors spaced along its length, wherein each of said jumper cablesincludes connector means at its other end for connection to any one ofsaid connectors, and wherein said circuit housing is operable to provideeasy access to said circuit means.
 4. A control circuit for operatingeach one of a plurality of strobe lights interconnected to form a systemin which the flashing thereof will occur in a desired manner comprising:trigger means for causing a strobe light to flash, input means forreceiving an external pulse from the control circuit of the precedingstrobe light, output means connected to said trigger means for supplyingan external pulse to the control circuit of the succeeding strobe lightwhenever said trigger means receives an actuating pulse, switching meansfor selectively connecting said input means to said trigger means sothat external pulses received by said input means may actuate saidtrigger means, and pulse generator means connected to said trigger meansfor providing an actuating pulse to said trigger means, said switchingmeans including means for controlling said pulse generator means tooperate as a master trigger actuating pulse generator when saidswitching means is in a mode causing said input means to be disconnectedfrom said trigger means, and fail safe means for controlling said pulsegenerator means to operate as a fail safe trigger actuating pulsegenerator when said switching means is in a mode causing said inputmeans to be connected to said trigger means.
 5. The circuit of claim 4wherein said pulse generator means includes a timing capacitor fordetermining the pulse rate thereof said timing capacitor beingdischarged whenever said trigger is actuated, and wherein said fail safemeans comprises a capacitor which is selectively connected in parallelwith said timing capacitor to reduce the pulse rate of said pulsegenerator means below the pulse rate of said external pulses when saidswitching means is operated to connect said input means to said triggermeans.
 6. The circuit of claim 4 wherein said input means includesdelaying means for delaying a received external pulse so as to actuatesaid trigger means after a time delay, when said input means isselectively connected through said switching means to create sequentialflashing of the strobe lights of the system.
 7. The circuit of claim 6wherein said input means further includes means for supplying a receivedexternal pulse to actuate said trigger means without a time delay, so asto create simultaneous flashing of the strobe lights of the system, andwherein said switching means may selectively connect either said delayedexternal pulse or said nondelayed external pulse or neither of saidpulses to said trigger means.